:Iron(II) bromide
{{chembox
| Verifiedfields = changed
| verifiedrevid = 432513551
| Name = Iron(II) bromide
| ImageFile1 = FeBr2(aq)4.svg
| ImageFile2 = Cadmium-iodide-3D-layers.png
| ImageName = Iron(II) bromide
| IUPACName = Iron(II) bromide
| OtherNames = Ferrous bromide
| SystematicName =
| Section1 = {{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 74218
| InChI = 1/2BrH.Fe/h2*1H;/q;;+2/p-2
| InChIKey = GYCHYNMREWYSKH-NUQVWONBAN
| SMILES = [Fe+2].[Br-].[Br-]
| SMILES_Comment = anhydrous
| SMILES1 = Br[Fe-4](Br)([OH2+])([OH2+])([OH2+])[OH2+]
| SMILES1_Comment = tetrahydrate
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/2BrH.Fe/h2*1H;/q;;+2/p-2
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = GYCHYNMREWYSKH-UHFFFAOYSA-L
| CASNo_Ref = {{cascite|correct|??}}
| CASNo1 = 20049-61-0
| CASNo1_Comment= tetrahydrate
| CASNo2 = 7789-46-0
| CASNo2_Comment= anhydrous
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = EA3X054RBZ
| PubChem = 425646
| RTECS =
}}
| Section2 = {{Chembox Properties
| Formula = FeBr2
| MolarMass = 215.65 g mol−1
| Appearance = yellow-brown solid
| Density = 4.63 g cm−3, solid
| Solubility = 117 g / 100 ml
| Solvent = other solvents
| SolubleOther = THF, methanol, ethanol
| MeltingPtC = 684
| MeltingPt_notes = (anhydrous)
27 °C (Hexahydrate)
| BoilingPtC = 934
| MagSus = +13,600·10−6 cm3/mol
}}
| Section3 = {{Chembox Structure
| Coordination = octahedral
| CrystalStruct = Rhombohedral, hP3, SpaceGroup = P-3m1, No. 164
| Dipole =
}}
| Section4 =
| Section5 =
| Section6 =
| Section7 = {{Chembox Hazards
| ExternalSDS =
| MainHazards = none
| FlashPt =
}}
| Section8 = {{Chembox Related
| OtherAnions = Iron(II) fluoride
Iron(II) chloride
Iron(II) iodide
| OtherCations = Manganese(II) bromide
Cobalt(II) bromide
| OtherFunction_label = compounds
| OtherFunction = Vanadium(II) bromide
Iron(III) bromide
}}
}}
Iron(II) bromide refers to inorganic compounds with the chemical formula FeBr2(H2O)x. The anhydrous compound (x = 0) is a yellow or brownish-colored paramagnetic solid. The tetrahydrate is also known, all being pale colored solids. They are common precursor to other iron compounds.
Structure
Like most metal halides, FeBr2 adopts a polymeric structure consisting of isolated metal centers cross-linked with halides. It crystallizes with the CdI2 structure, featuring close-packed layers of bromide ions, between which are located Fe(II) ions in octahedral holes.{{cite journal|doi=10.1524/ncrs.2001.216.14.544|title=Refinement of the crystal structure of iron dibromide, FeBr2|journal=Zeitschrift für Kristallographie - New Crystal Structures|volume=216|issue=1–4|year=2001|last1=Haberecht|first1=J.|last2=Borrmann|first2=Η.|last3=Kniep|first3=R.|doi-access=free}} The packing of the halides is slightly different from that for FeCl2, which adopts the CdCl2 motif. The tetrahydrates FeX2(H2O)4 (X = Cl, Br) have similar structures, with octahedral metal centers and mutually trans halides.{{cite journal |doi=10.1016/S0020-1693(00)80756-2| title=X-ray Structural Studies of FeBr2·4H2O, CoBr2·4H2O, NiCl2·4H2O and CuBr2·4H2O. Cis/Trans Selectivity in Transition Metal(II) Dihalide Tetrahydrate | year=1992 | last1=Waizumi | first1=Kenji | last2=Masuda | first2=Hideki | last3=Ohtaki | first3=Hitoshi | journal=Inorganica Chimica Acta | volume=192 | issue=2 | pages=173–181 }}
Synthesis and reactions
FeBr2 is synthesized using a methanol solution of concentrated hydrobromic acid and iron powder. It adds the methanol solvate [Fe(MeOH)6]Br2 together with hydrogen gas. Heating the methanol complex in a vacuum gives pure FeBr2.{{cite book|doi=10.1002/9780470132456.ch20|chapter=Iron(II) Halides|pages=99–104|year=1973|volume=14| last1=Winter|first1=G.|title=Inorganic Syntheses|isbn=9780470132456}}
FeBr2 reacts with two equivalents of tetraethylammonium bromide to give [(C2H5)4N]2FeBr4.N. S. Gill, F.. B. Taylor Inorganic Syntheses 1967, volume 9, page 136-142. {{doi| 10.1002/9780470132401.ch37}} FeBr2 reacts with bromide and bromine to form the intensely colored, mixed-valence species [FeBr3Br9]−.Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. {{ISBN|0-12-352651-5}}
Magnetism
FeBr2 possesses a strong metamagnetism at 4.2 K and has long been studied as a prototypical metamagnetic compound.{{cite journal |last1=Wilkinson |first1=M. K. |last2=Cable |first2=J. W. |last3=Wollan |first3=E. O. |last4=Koehler |first4=W. C. |title=Neutron Diffraction Investigations of the Magnetic Ordering in FeBr2, CoBr2, FeCl2, and CoCl2 |journal=Physical Review |date=15 January 1959 |volume=113 |issue=2 |pages=497–507 |doi=10.1103/PhysRev.113.497|bibcode=1959PhRv..113..497W }}{{cite journal |last1=Jacobs |first1=I. S. |last2=Lawrence |first2=P. E. |title=Metamagnetic Phase Transitions and Hysteresis in FeCl2 |journal=Physical Review |date=10 December 1967 |volume=164 |issue=2 |pages=866–878 |doi=10.1103/PhysRev.164.866|bibcode=1967PhRv..164..866J }}
References
{{Iron compounds}}
{{Bromides}}